You’ve chosen Grotek nutrients and you’re wondering what to add, how much and in which week? The Grotek feed chart answers all three. Grotek publishes official feeding charts for its two base ranges, Solo-Tek and Impact A+B. We’ve brought them together here, with doses converted to millilitres per litre, the target conductivity (EC) for each stage and our tips for adapting them to your grow. As a bonus, there’s a Grotek feed chart for autoflowers that you won’t find anywhere else.
How to read a Grotek feed chart
All Grotek charts follow the same logic, in two main blocks.
- Growth, in four stages: seedling (or clone), transplant, vegetative and pre-flower, just before the switch to 12/12.
- Flowering, over eight weeks: seven weeks of feeding, then week 8 set aside for flushing with Final Flush.
For each stage, the chart gives the dose of each product and the total EC of the solution. These EC values are based on reverse-osmosis water: if your tap water already has a starting EC, add it to the chart values.
Watch the units. The official Solo-Tek chart is given per 4 litres of water, the Impact charts in millilitres per litre. In our versions below, everything is converted to ml/L (or g/L for powders).
Grotek Solo-Tek feed chart: one-part base nutrients
The brand’s simplest programme. Solo-Tek Grow for growth, Solo-Tek Bloom for flowering, with Grotek supplements around them.
| Product (per litre) | Seedling | Transpl. | Veg | Pre-flower | Wk 1 | Wk 2 | Wk 3 | Wk 4 | Wk 5 | Wk 6 | Wk 7 | Wk 8 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solo-Tek Grow | 0.5 ml | 1 ml | 2 ml | 2 ml | – | – | – | – | – | – | – | – |
| Solo-Tek Bloom | – | – | – | – | 2 ml | 2 ml | 2 ml | 2 ml | 2 ml | 2 ml | 2 ml | – |
| Vitamax Pro | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | – |
| Bud Fuel Pro | – | – | – | – | 2 ml | 2 ml | 2 ml | 1 ml | – | – | – | – |
| Monster Bloom | – | – | – | – | – | – | – | 0.1 g | 0.2 g | 0.1 g | 0.1 g | – |
| Heavy Bud Pro | – | – | – | – | – | – | – | 1 ml | 2.75 ml | 2.75 ml | 2 ml | – |
| Pro-Silicate | 0.25 ml | 0.5 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | – |
| Final Flush | – | – | – | – | – | – | – | – | – | – | – | approx. 2 ml |
| EC (mS/cm) | 0.6 | 0.9 | 1.7 | 1.9 | 1.9 | 1.9 | 1.9 | 2.0 | 2.2 | 2.1 | 2.0 | – |
Grotek’s tips for this programme:
- Feed once a week, allowing 10–15% run-off from the bottom of the pot.
- For calcium- or magnesium-hungry plants, add Cal-Max: 4–8 ml per gallon, roughly 1–2 ml per litre.
- Pro-Silicate raises pH: dilute it in the water first, before other nutrients. The official chart lists GroSilic as an alternative silicon source.
- In living soil, Grotek suggests amending the medium with its Synergy, Biofuse or Black Pearl products.
Grotek Impact A+B feed chart: the full programme
The Impact programme is built on two-part base nutrients: Impact Grow A+B for growth and Impact Bloom A+B for flowering. It’s Grotek’s most complete chart, using every supplement in the range.
| Product (per litre) | Seedling | Transpl. | Veg | Pre-flower | Wk 1 | Wk 2 | Wk 3 | Wk 4 | Wk 5 | Wk 6 | Wk 7 | Wk 8 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Impact Grow A | 1 ml | 1.5 ml | 2.5 ml | 2 ml | – | – | – | – | – | – | – | – |
| Impact Grow B | 0.5 ml | 1 ml | 2 ml | 2.5 ml | – | – | – | – | – | – | – | – |
| Impact Bloom A | – | – | – | – | 2 ml | 2 ml | 2 ml | 2 ml | 2 ml | 2 ml | 0.5 ml | – |
| Impact Bloom B | – | – | – | – | 2.5 ml | 2 ml | 2 ml | 2 ml | 2 ml | 2 ml | 1 ml | – |
| Vitamax Pro | – | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | – |
| Bud Fuel Pro | – | – | – | 1 ml | 1 ml | 1 ml | 1 ml | – | – | – | – | – |
| Monster Bloom | – | – | – | – | – | – | – | 0.1 g | 0.1 g | 0.1 g | 0.1 g | – |
| Heavy Bud Pro | – | – | – | – | – | – | – | 1 ml | 2 ml | 2 ml | 2 ml | – |
| Pro-Silicate | 0.25 ml | 0.5 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | – |
| Cal-Max | 0.5 ml | – | 1 ml | 2 ml | 1 ml | 1 ml | 1 ml | – | 1 ml | 1 ml | – | – |
| Carbo-Max | – | – | – | – | – | – | – | – | – | 1 g | 1 g | – |
| Final Flush | – | – | – | – | – | – | – | – | – | – | – | 2 ml |
| EC (mS/cm) | 1.0 | 1.3 | 2.4 | 2.9 | 2.4 | 2.3 | 2.3 | 2.0 | 2.5 | 2.6 | 1.3 | – |
This chart uses almost the whole range: Vitamax Pro throughout, Bud Fuel Pro around the switch to flowering, Monster Bloom and Heavy Bud Pro from week 4 to week 7, Pro-Silicate for sturdy stems and Carbo-Max in late flowering.
Grotek Impact feed chart: base nutrients only
New to Grotek, or prefer a minimal programme? Grotek also offers an Impact chart with just the A+B bases and the flush, no supplements. Base doses are slightly higher to make up for the missing boosters.
| Product (per litre) | Seedling | Transpl. | Veg | Pre-flower | Wk 1 | Wk 2 | Wk 3 | Wk 4 | Wk 5 | Wk 6 | Wk 7 | Wk 8 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Impact Grow A | 1 ml | 1 ml | 2.5 ml | 2 ml | – | – | – | – | – | – | – | – |
| Impact Grow B | 0.5 ml | 1 ml | 2 ml | 2.5 ml | – | – | – | – | – | – | – | – |
| Impact Bloom A | – | – | – | – | 2 ml | 2 ml | 2 ml | 2.5 ml | 2 ml | 2 ml | 0.5 ml | – |
| Impact Bloom B | – | – | – | – | 2 ml | 2.5 ml | 2 ml | 2.5 ml | 2.5 ml | 2.5 ml | 1 ml | – |
| Final Flush | – | – | – | – | – | – | – | – | – | – | – | 2 ml |
| EC (mS/cm) | 0.7 | 0.9 | 2.0 | 1.8 | 1.5 | 1.7 | 1.5 | 1.8 | 1.7 | 1.7 | 0.6 | – |
Adapting the chart to flowering time
Grotek’s charts are built around an 8-week flowering period, or 56 days. For longer strains, Grotek recommends:
- 56 days: flush with Final Flush and water in week 8.
- 63 days: repeat week 7, then flush in week 9.
- 70 days: repeat week 7 twice, then flush the following week.
Grotek feed chart for autoflowers
Grotek doesn’t publish an official chart for autoflowering strains. Yet an auto doesn’t feed like a photoperiod plant: it starts flowering on its own after 3–4 weeks, whatever the light schedule, and finishes in 9–11 weeks from seed. There’s no time for a long veg, and little room to correct overfeeding.
So we’ve adapted the official Solo-Tek chart to a 10-week auto cycle: same products, same stages, but doses about 25% lower and a shorter growth phase.
| Product (per litre) | Wk 1 | Wk 2 | Wk 3 | Wk 4 | Wk 5 | Wk 6 | Wk 7 | Wk 8 | Wk 9 | Wk 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Stage | Seedling | Growth | Growth | Pre-flower | Flowering | Flowering | Bulking | Bulking | Ripening | Flush |
| Solo-Tek Grow | 0.5 ml | 1 ml | 1.5 ml | 1 ml | – | – | – | – | – | – |
| Solo-Tek Bloom | – | – | – | 0.5 ml | 1.5 ml | 1.5 ml | 1.5 ml | 1.5 ml | 1 ml | – |
| Vitamax Pro | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | 1 ml | – | – |
| Bud Fuel Pro | – | – | – | 1 ml | 1 ml | 1 ml | – | – | – | – |
| Monster Bloom | – | – | – | – | – | – | 0.1 g | 0.1 g | – | – |
| Heavy Bud Pro | – | – | – | – | – | – | 1 ml | 1.5 ml | 1.5 ml | – |
| Pro-Silicate | 0.25 ml | 0.5 ml | 0.75 ml | 0.75 ml | 0.75 ml | 0.75 ml | 0.75 ml | 0.75 ml | – | – |
| Final Flush | – | – | – | – | – | – | – | – | – | 2 ml |
| Max. recommended EC | 0.6 | 0.8 | 1.2 | 1.4 | 1.5 | 1.6 | 1.7 | 1.7 | 1.3 | – |
How to use it:
- Week 4, the transition: mix a little Grow and Bloom, because autos switch to flowering without warning. As soon as you see the first pistils, move to the week 5 column.
- Pre-fertilised soil (“all mix” type): don’t start feeding until week 3. With a light mix or coco, follow the chart from week 1.
- Avoid stress: autos don’t recover well. If leaf tips burn, skip a feed and go back to the previous column.
- Longer cycle (11 weeks or more): repeat week 8 before ripening.
- Optional: Blossom Blaster Pro at 1 ml/L in weeks 5 and 6 to support early flower set.
This chart is our adaptation of Grotek’s official doses, not a manufacturer document. Treat it as a guide: your strain, pot size and lighting matter as much as the calendar.
Monster Bloom dosage
Monster Bloom is Grotek’s best-known booster, and also the one that raises the most dosage questions.
- Powder (NPK 0-50-30): 0.1 g per litre in the Impact charts, and up to 0.2 g per litre in week 5 of the Solo-Tek chart. Weigh it on precision scales. Without scales, Grotek gives this equivalent: 0.4 g per gallon is 1/3 teaspoon per 5 gallons (about 19 litres).
- Liquid (NPK 0-10-6): Monster Bloom Liquid is dosed at 1 ml per litre with every feed during flowering, until 1–2 weeks before harvest.
The two versions have different concentrations: never swap one for the other at the same dose.
Mixing your nutrient solution
- Pro-Silicate first, into plain water, then stir.
- Cal-Max next, especially with RO water.
- Your base: Solo-Tek, or Impact A then B, stirring in between. Never mix A and B neat.
- Supplements and boosters last.
- Check EC and pH: about 6.0–6.5 in soil, 5.5–6.2 in coco and hydroponics.
If leaf tips burn, cut doses by about 25%. The chart EC values are maximums, not targets you must hit.
Which Grotek feed chart should you choose?
- You want simplicity: Solo-Tek, one bottle per phase.
- You want fine control: Impact A+B with supplements.
- You’re new to Grotek: Impact base only, then add one booster at a time on your next grow.
- You grow autos: our Grotek feed chart for autoflowers, based on Solo-Tek.
Every product mentioned is in our Grotek nutrients category.
Grotek feed chart FAQ
Does the Grotek feed chart work in soil?
Yes. The charts are designed for all growing media. In rich soil, start lower, around half the doses, since the medium already supplies nutrients.
Is there an official Grotek feed chart for autoflowers?
No, Grotek only publishes charts for photoperiod strains. Our autoflower chart uses the official products and doses, reduced and adapted to a 10-week cycle.
Why is the chart EC higher than mine?
The EC values shown are maximums, calculated with RO water. You don’t have to reach them: if your plants are happy at a lower EC, stay there.
Can I mix Solo-Tek and Impact?
No. Pick one base for the whole grow. The supplements, however, work with both.
Do I need every product on the chart?
No. Only the base is essential. Then add supplements as needed: Cal-Max with RO water or in coco, Pro-Silicate in hydroponics, Monster Bloom for flowering.
